Pulse amplifier



Feb. 18, 1947.' R. B. NELSON PULSE AMPLIFIER Filed Aug. 3, 1944UTILIZATION DEV/CE UTIL/ZAT/OA/ DEVICE PULSE... sauna:

Inventor: Richard BNeIson,

His Attorn ey.

Patented Feb. 18, 1947 PULSE AMPLIFIER Richard B. Nelson, Schenectady,N. Y., assignor to General Electric Company, a corporation of New YorkApplication August 3, 1944, Serial No. 547,872

8 Claims.

This invention relates to devices for amplifying electn'cal pulses andparticularly to electronic pulse amplifiers of the type adapted to drawcurrent only durin the amplification of the pulses.

In apparatus such as radio locating and range finding devices whichemploy electrical pulses of short duration, it is desirable that theamplifiers used be provided with electron discharge devices or tubeswhich are conducting only durin the amplification f the pulses so thatminimum power is required and longer life of the tubes is possible. Inorder to render the electron discharge devices conducting only duringthe amplification of the pulses, the several devices are biased beyondcutoff so that only a pulse in the positive sense will render thedevices conducting. Obviously it is necessary to invert the pulsesbetween any two stages in order to provide a positive pulse to renderconducting the electron discharge device of the second stage. Thisinversion of the pulses has been accomplished, for example, by the useof pulse transformers between the stages. However, these transformershave not been entirely satisfactory because of some resulting distortionof the wave form of the pulses. Accordingly, it is an object of thisinvention to provide a pulse amplifier including an improved arrangementfor minimizing the power consumption of the amplifier while maintainingthe desired pulse wave form.

It is another object of this invention to provide a pulse amplifier or"the type which employs normally nonconducting electron discharge devicesand includes an improved arrangement for facilitating amplification ofpulses without distortion and. with a predetermined time delay.

The novel features which are believed to be characteristic of thisinvention are set forth with particularity in the appended claims. Theinvention itself, however, both as to its organization and method ofoperation, together with further objects and advantages thereof, maybest be understood by reference to the following description taken inconnection with the accompanying drawing in which Fig. 1 represents oneembodiment of the invention; Fig. 2 illustrates graphically the mannerof operation of the amplifier of Fig. l; and Fig. 3 represents anotherernbodi ment of the invention.

Referring now to Fig. l, the pulse amplifier illustrated compriseselectron discharge devices l and 2 connected to provide two stages ofampli fication between a suitable source of pulses 3 and a utilizationdevice 4. The device I is provided with a cathode 5, an anode 6 and acontrol electrode 1. The pulses generated by the apparatus 3 areimpressed on the control electrode 7 across a suitable resistor 8. Asuitable negative bias voltage is provided for the electrode 7 to renderthe device i normally non-conducting and, in the embodiment shown, abattery 9 has been illustrated for providing the bias. The generatingapparatus It is arranged to impress the pulses on the control electrode1 in a positive sense so that the device l is rendered conducting forthe duration of each pulse. The anode 6 is connected through a resistorit to a suitable source of anode potential indicated as a battery I 1.

When a positive pulse as indicated at l2 in 2 is impressed on thecontrol electrode 1 with sunicient intensity, it overcomes the bias ofthe device l to render the device conducting and produces a negativepulse across the resistor it! as indicated at i3 in the middle curve ofFig. 2. The anode 5 of the device i is coupled through a capacitor hiand a resistor to the control electrode of the device 2 indicated at to.The device 2 is provided with a cathode ll and an anode i8, and theutilization device is connected in the anode tmcathode circuit of thedevice 2 in any suitable manner. The device 2 is biased to be normallynonconducting by a battery :9 connected between the cathode i? andcontrol electrode it to maintain a negative bias on the controlelectrode, this being the bias indicated in the middle curve of Fig. 2.When the negative pulse i3 is impressed on the control electrode IE, ithas no eifect on the device 2, which K remains nonconducting. In orderto provide a positive pulse of the same wave form and duration as thepulse 52 and to impress this pulse on the control electrode 56, anartificial transmission line 29 is connected with its input terminalsacross the resistor l5 and with its terminals at the other end shortcircuited. When the pulse I3 is impressed on the transmission lineacross the resistor is, it travels down the line to the short-circuitedend where it is reflected in the inverted sense and returns to appearacross resistor is as a positive pulse as indicated at 25 in Fig. 2. Thepulse 26 is of sufiicient intensity to overcome the bias of the device 2and render the device conducting so that a negative pulse appears at theoutput of the device 2 as indicated at 22 in Fig. 2. The pulses 2i and22 are delayed a predetermined interval of time de pending upon the timeconstant of the transmission line 28, the length of time between thebeginning of the pulse l3 and the beginning of the pulse 2! being equalto twice the time constant of the line. The resistor it is selected tohave a value equal to the characteristic impedance of the transmissionline 2c in order to prevent any further reflections of the pulse afterit has returned to the resistor it from the far end of the line. Thewave form of the pulse produced at the output of the device 2 is thesame as that or the pulse impressed on the control electrode 7 of thedevice is. The time constant of the transmission line is selected to beof any suitable value greater than the duration of the pulse anddependent upon the delay desired in the particular apparatus with whichthe amplifier is being employed. It will readily be understood by thoseskilled in the art that such a time delay may be desirable, for example,in ap paratus employing cathode ray signal portraying tubes in order toinsure the initiation of the cathode ray sweep before the occurrence ofthe signal pulse which it is desired to observe. It is also obvious thatany type of artificial transmission line may be employed which iscapable of producing the desired time delay.

The embodiment of the invention illustrated in Fig. 3 is similar to thatillustrated in Fig. 2 and corresponding parts have been designated bythe same numerals. The modification of Fig. 3 diffrom that of Fig. 2 inthat a four terminal symmetric transmission line is employed asindicated at 23. A transmission line of this type comprises twoconductors each of which is a symmetric part of the circuit, the twoconductors having equal series impedance. The two terminals at the inputend of the transmission line 23 are connected across th resistor it, theupper terminal being connected to the anode ii and the lower terminal toa suitable point of fixed. reference potential, such as ground, througha bypass condenser 2d. At the other or output end of the transmissionline 23 the conductor which is connected to the anode 5 at its input endis connected to ground, while the conductor which is grounded at theinput end is coupled to the control electrode it of the device 2 througha condenser 25 and the resistor E5. The time constant of thetransmission line 23 is selected to be equal to the total delay timerequired between the pulse at the input of the device I and the pulse atthe output of the device 2. The operation of the embodiment of Fig. 3 isthe same as that of the embodiment of Fig. 1 and the curves of Fig. 2may considered as representing the operation of the circuit of Fig. 3.When the negative pulse 13 is impressed across the resistor it in Fig.3, it appears simultaneously at the output end of the transmission lineso that it is impressed on the control electrode It but has no eifectupon the device 2. The pulse is is followed after a delay determined bythe time constant of the transmission line 23 by the inverted pulse 2!in the positive sense which renders the device 2 con ducting so that theamplified pulse 22 appears at the output of the device 2. The delayedpulse 2! is inverted because of the reversed connections of theterminals at the output of the transmission line, the voltage appearingbetween ground and the control electrode it in the opposite sense fromthat in which it was impressed across t-e resistor iii. The appearanceof the negative pulse it simultaneously across resistor it and at thecontrol electrode it occurs because the ground connection provides ineffect a,third conductor for the transmission line.

In the foregoing it is readily apparentthat there has been provided asimple and efiective amplifier for reproducing a signal pulse in thesame wave form with a predetermined time delay while maintaining theelectron discharge devices of the amplifier normally nonconducting.

While particular embodiments of the invention have been illustrated anddescribed, other applications will readily be apparent to those skilledin the and it is intended by the appended claims to cover allmodifications which fall within the spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

A pulse amplifier comprising means for generating a signal pulse in anegative sense, means for amplifying a signal pulse which is impressedthereon in a positive sense, and means including a transmission lineconnected to said generating means and to said amplifying means forimpressing the generated pulse both simultaneously in the samesense andafter a predetermined time interval in the opposite sense on saidamplifying means whereby said amplifying means amplifies and reproducessaid negative signal pulse a predetermined time interval after thegeneration thereof.

2. A pulse amplifier comprising first and second electron dischargedevices each having a cathode and an anode and a control electrode,means for impressing on the control electrode of said first device asignal pulse to be amplified whereby said pulse appears simultaneouslyin an inverted sense at the anode of said first device, and meansincluding a transmission line connected to the anode of said firstdevice and to the control electrode of said second device for impressingthe amplified pulse both simultaneously in the same sense and after apredetermined delay in the opposite sense on the control electrode ofsaid second device.

3. A pulse amplifier comprising first and second electron dischargedevices each having a cathode and an anode and a control electrode,means for impressing on the control electrode of said first device asignal pulse to be amplified, means including a transmission line havinga predetermined time delay for coupling the anode of said first deviceand the control electrode of said second device whereby said pulse isamplified by said first device and appears in an inverted sense on thecontrol electrode of said second device simultaneously and is followedat the end of a period determined by the time delay of said transmissionline by a second pulse on the control electrode of said second deviceand in the same sense as the original pulse.

4. A pulse amplifier comprising first and second electron dischargedevices each having a cathode and an anode and a control electrode andeach biased to be normally nonconducting, means for impressing on thecontrol electrode of said first device and in a positive sense a signalpulse to be amplified whereby said pulse appears simultaneously in aninverted sense at the anode of said first device, and means including atransmission line connected to the anode of said first device and to thecontrol electrode of said second device for impressing the amplifiedpulse both simultaneously in the same sense and after a predetermineddelay in the opposite sense on the control electrode of said seconddevice whereby said second device is rendered conducting to amplify andreproduce said pulse at the anode of said second device a predeterminedtime after the impressing of said pulse on the control electrode of saidfirst device.

5. A pulse amplifier comprising first and second electron dischargedevices each having a cathode and an anode and a control electrode andeach biased to be normally nonconducting, means for impressing on thecontrol electrode of said first device and in a positive sense a signalpulse to be amplified, a resistor connected between the anode andcathode of said first device whereby said pulse is amplified and appearsin an inverted sense across said resistor, a transmission line havingterminals at one end connected across said resistor for producing adelayed pulse in the opposite sense from the pulse across said resistor,said resistor having an impedance equal to the characteristic impedanceof said line, and means for impressing said delayed pulse on the controlelectrode of said second device whereby said original signal pulse isamplified and appears in an inverted sense at the anode of said seconddevice a predetermined interval after it is impressed on the controlelectrode of said first device.

6. A pulse amplifier comprising first and second electron dischargedevices each having a cathode and an anode and a control electrode andeach biased to be normally nonconducting, means for impressing on thecontrol electrode of said first device and in a positive sense a signalpulse to be amplified, means for coupling the anode of said first deviceand the control electrode of said second device, a resistor connectedbetween the anode and the cathode of said first device, and atransmission line having terminals at one end connected across saidresistor and having its terminals at the other end short circuitedwhereby the pulse appearing at the anode of said first device isinverted and impressed after a predetermined time upon the controlelectrode of said second device to render said second device conductingand to reproduce said pulse with substantially the same wave form at theanode of said second device.

7. A pulse amplifier comprising first and second electron dischargedevices each having a cathode and an anode and a control electrode,means for impressing on the control electrode of said first device asignal pulse to be amplified, means including a two-conductor symmetrictransmission line arranged to couple the anode of said first device andthe control electrode of said second device for impressing the amplifiedpulse on the control electrode of said second device in an invertedsense and after a predetermined time delay, one of the conductors ofsaid transmission line being connected at the input end of said line tothe anode of said first device and at the output end to a point of fixedreference potential, the other conductor of said transmission line beingconnected at the input end to a point at said fixed reference potentialand at the output end to the control electrode of said second device,and a resistor having an impedance equal to the characteristic impedanceof said transmission line connected between said two conductors at oneof said ends of said line.

8. A pulse amplifier comprising first and second electron dischargedevices each having a cathode and an anode and a control electrode andeach biased to be normally nonconducting, means for impressing on thecontrol electrode of said first device and in a positive sense a signalpulse to be amplified, a resistor connected between the anode and thecathode of said first device and having its end remote from said anodeconnected to a point of fixed reference potential, means including atwo-conductor symmetric transmission line having its input terminalsconnected across said resistor and its output terminals connectedbetween the control electrode and cathode of said second device forimpressing the amplified pulse delayed and in an inverted sense on thecontrol electrode of said second device, one of the conductors of saidline having its input end connected to a point at said fixed referencepotential and the other conductor having its output end connected to apoint at said fixed reference potential, said resistor having animpedance between said input terminals equal to the characteristicimpedance of said line,

RICHARD B. NELSON.

